Core Java — JavaBeans

JavaBeans are java classes which are created as per following conventions

1. It must have a zero-argument public constructor.
2. It must provide getter-setter methods to access private instance variables.
3. It must implement Serializable interface.

Let’s create a Java class according to these rules.

import java.io.Serializable;
public class Employee implements Serializable {
   private Integer id;
   private String firstName;
   private String lastName;
   private Double salary;
   public Employee() {
   }
   public Integer getId() {
      return this.id;
   }
   public void setId(Integer id) {
      this.id = id;
   }
   public String getFirstName() {
      return this.firstName;
   }
   public void setFirstName(String firstName) {
      this.firstName = firstName;
   }
   public String getLastName() {
      return this.lastName;
   }
   public void setLastName(String lastName) {
      this.lastName = lastName;
   }
   public Double getSalary() {
      return this.salary;
   }
   public void setSalary(Double salary) {
      this.salary = salary;
   }
}

Now, we can call Employee class a JavaBean.

Some uses of JavaBeans

1. We can create a list of employee by reading their data from the database.

List<Employee> employeeList = new ArrayList<>();
while(resultSet.next()) {
   Employee employee = new Employee();
   employee.setId(resultSet.getInteger("id"));
   employee.setFirstName(resultSet.getString("firstname"));
   employee.setLastName(resultSet.getString("lastname"));
   employee.setSalary(resultSet.getDouble("salary"));
   employeeList.add(employee);
}
return employeeList;

2. We can transfer employees data from servlet doGet/doPost methods to JSP page for rendering it as HTML.

protected void doGet(HttpServletRequest request, HttpServletResponse response) {
   List<Employee> employeeList = employeeDAO.getAllEmployees;
   request.setAttribute("employees", employeeList);
   request.getRequestDispatcher("employees.jsp").forward(request,
   response);
}

In JSP page

<table>
    <tr>
        <th>ID</th>
        <th>Name</th>
        <th>Salary</th>
    </tr>
    <c:forEach items="${employees}" var="employee">
        <tr>
            <td>${employee.id}</td>
            <td>${employee.firstname}&nbsp;${employee.lastname}</td>
            <td>${employee.salary}</td>
        </tr>
    </c:forEach>
</table>

JavaBeans are often used to represent real world data. It is easy to store, transfer and access the data if we use JavaBeans specification.